A computational fingerprint that uniquely characterises William Shakespeare's writing style is helping to dispel any lingering doubts that he penned his own plays.

The method could analyse not only plays attributed to Shakespeare but anonymous or controversial writings by other authors.

"People will take these programs and use the design to go to the 19th century and talk about Lord Byron," says Professor Arthur Kinney, director of the Massachusetts Center for Renaissance Studies at the University of Massachusetts, Amherst.

Kinney leads the research with Australia's Professor Hugh Craig, director of the Centre for Literary and Linguistic Computing at the University of Newcastle.

The researchers built a massive database containing tens of thousands of words from Shakespeare's works as well the works of other playwrights of his time.

Then they used a method called computational stylistics to analyse the usage, occurrence, spelling and placement of phrases, as well as common and rare words.

For example, the word 'gentle' appears almost twice as frequently in works by Shakespeare than in works by other writers. And Shakespearean drama frequently finds the word 'farewell' preceded by 'hail'.

A computational fingerprint is created from known works and then compared with the fingerprints of unknown works to see if there is a match.

Doubts

Controversy over whether Shakespeare, an ordinary, working class man from the countryside, could have authored such remarkable writing began percolating in the middle of the 19th century.

Those who doubt his ability suggest that another, more educated man, such as the Earl of Oxford, Edward deVere, penned the plays. Why would the Earl attribute them to Shakespeare? To deflect criticism, some claim.

During the early part of the 1600s, the gathering of a large crowd at a theatre signalled political unrest and made government officials nervous. And Christian groups, such as the Puritans, found the theatre immoral.

But there has been plenty of evidence to suggest that Shakespeare did write the plays.

For one, Shakespeare apparently wrote plays until 1611; the Earl of Oxford died in 1601.

Also, at least four different publishers put Shakespeare's dramas to print. If he had not been the author, they would have all had to keep the secret.

"The more people you had to have involved [in the conspiracy], the more likely it would have been that somebody would have blown the whistle," says Professor Gary Taylor, director of History of Text Technologies at Florida State University.